The worst DVDs i've seen for pathetic PQ are most definitely:
Germany's Red Edition
Nightmare City, the U.K. Hollywood DVD print of
The Grim Reaper, Troma's original release of
Fanatic
(aka.
The Last Horror Film and Intervision's VHS pre-cert looked better imo!) and the ancient fullscreen Canadian versions of
Day Of The Animals and
Grizzly.
No doubt there's a veritable ocean of teeth-grindingly bad DVD transfers out there and the many titles mentioned in this thread are just the tip of the ire-inducing iceberg.